pinctrl: meson: gxl: add the missing PWM pin definitions

This adds support for the missing PWM pins on Meson GXL SoCs, namely:
- PWM_A
- PWM_B
- PWM_C
- PWM_F (GPIOX_7 and GPIOCLK_1 can be selected as output)
- PWM_AO_A (GPIOAO_3 and GPIOAO_8 can be selected as output)

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Tested-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>